As materials used for sliding members (rings) of mechanical seals include a variety of combinations of silicon carbide sintered bodies, carbon bodies, cemented carbide bodies, alumina sintered bodies and the like.
When sliding members made of combinations of silicon carbide bodies and another silicon carbide bodies enable use at higher PV limiting value, a high PV limit enables an increased performance and miniaturization of the sealing device and the apparatus using same. Further, combinations of two silicon carbide sliding members are frequently used where there is a problem in particle wear due to handling of the slurry. Also, in a usage at high PV value, combinations of cemented carbide bodies and bonded carbon bodies, or cemented carbide bodies and cemented carbide bodies and the like are used.
However, when a surface of a silicon carbide sliding member comes into contact with a surface of another silicon carbide sliding member, problems such as abnormal noise (sneaking) and linking easily occur at the startup period. Further, when a surface of a carbon material sliding member comes into contact with a surface of another silicon carbide sliding member, carbon blisters which advance to formation of microcracks and finishes with worm defects sometimes appear on the sliding surface of the carbon material member. Furthermore, when sliding members made of combinations of cemented carbide bodies and another carbon material are used in a freezer and the like, in addition to requiring a high PV value, a large thermal shock is experienced at the startup period because of the repetition of running and stopping, and there are problems such that heat cracks are produced in the sliding surface, and that with carbon material bulges are produced.
In order to respond to such problems, it is disclosed that a sliding member of a seal device is made of a silicon carbide sintered body having pores with suitable ranges of pore diameter and porosity, in which the pores serve liquid reservoirs extruding liquid impregnated therein upon frictional heat at startup to form a liquid film for lubrication (refer to Japanese Patent examined Publication No. H5-69066 (Patent Document 1)).
Also, it is disclosed that a mechanical seal which is, at least at the seal surface and its vicinity, formed of a pre-dispersed material wherein the pores are generally dispersed, and the lubricating characteristics can be improved and the strength is maintained by strictly stipulating the shape and the like of pores (refer to Japanese Patent examined Publication No. H07-88909 (Patent Document 2)).    Patent Document 1: JP Patent examined Publication No. H05-69066    Patent Document 2: JP Patent examined Publication. No. H07-88909
However, in recent years, sliding condition of the mechanical seal becomes more severe, many proposals have been presented to increase the lubricating ability of sliding surface of a sliding member.